1. Field of the Invention
The present invention relates generally to disconnect devices for use in wellbore tools, and specifically to disconnect devices for use in setting tools which are suspended in a wellbore on an electric wireline, or tubular work string.
2. Description of the Prior Art
Work strings and wireline tools are frequently used to position, actuate, and operate wellbore tools, and are especially useful in positioning and actuating fluid-actuated wellbore tools, such as packers, liner hangers, and bridge plugs. However, a work string or wireline tool frequently includes subassemblies which are intended for temporary or permanent placement within the wellbore, as well as subassemblies which are intended for retrieval from the wellbore for subsequent use. For example, many inflatable packers, bridge plugs, and liner hangers are adapted for permanent placement within a wellbore. However, the tools which cooperate in the placement and actuation of such permanently-placed wellbore devices are frequently not suited for permanent placement in the wellbore. For example, sources of pressurized fluid, such as retrievable wellbore pumps, have great economic value, and are not intended for a single, irretrievable use in a wellbore. Therefore, disconnect devices exist which serve to separate a upper retrievable portion of a work string or wireline tool from a lower "delivered" portion which is intended for permanent or temporary placement in the wellbore. One such device is a hydraulically actuated disconnect for disconnecting the upper retrievable portion from the lower delivered portion. Since the hydraulic disconnect is susceptible to failure, it is prudent to provide other, alternative disconnect mechanisms. The present invention is directed to a pull release apparatus which is adapted for use in a wellbore when coupled between a fluid-actuated wellbore tool and a retrievable source of pressurized fluid. The present invention may operate alone or in combination with other disconnect devices to ensure that valuable retrievable tools are not irretrievably placed or positioned within the wellbore. This avoids the unintended loss of rather expensive and useful wireline and work string tools.